Partial purification and kinetic characterization of transaldolase fromDictyostelium discoideum |
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Affiliation: | 1. Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN 37232-8548, United States;2. Department of Psychiatry, Vanderbilt University Medical Center, Nashville, TN 37232-8548, United States;3. Department of Biology, Fisk University, Nashville, TN 37208, United States;4. Department of Biomedical Sciences, Charles E. Schmidt College of Medicine, Jupiter, FL 33458, United States |
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Abstract: | Transaldolase was purified 42-fold fromDictyostelium discoideum and the resulting preparation exhibited stoichiometry. Kinetic analyses consisted of initial velocity and product inhibition studies in both the forward and the reverse directions. The enzyme exhibited ping-pong kinetics with sedoheptulose 7-phosphate adding first and erythrose 4-phosphate releasing first. TheKm values for sedoheptulose 7-phosphate, glyceraldehyde 3-phosphate, erythrose 4-phosphate, and fructose 6-phosphate were 0.46, 0.072, 0.10, and 1.6 mM, respectively. TheKi values for sedoheptulose 7-phosphate and erythrose 4-phosphate were 3.6 and 0.062 mM, respectively. Inorganic phosphate inhibited enzymatic activity and showed mixed-type inhibition when fructose 6-phosphate was varied. AKi value of 35.2 mM was determined for inorganic phosphate. |
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